1. Plate Tectonics
Earth Science
Charlotte Carter

2. Unit Review

3. Drifting Continents Evidence of drifting
Fossils found on both of the continents of Africa and South America that are of the same organism
Fossils: The preserved remains of ancient organisms
German scientist Alfred Wegner came up with the theory of continental drift, he was actually a meteorologist and not a geologist
The theory called the giant landmass that once was on Earth Pangaea
Pangaea: Means all Earth
Early Earth & Plate Tectonics

4. Fossil Evidence
Fossils play a key role in supporting the theory of Continental drift
Glossopteris is an extinct plant
They are found in rocks that are around 250,000,000 years old ( 250 million)
The seeds were to large to be carried by wind and too fragile to have survived ocean waves
The fact that they are found in Antarctica implies that they had to be in a better climate than what is present Antarctica

5. Fossils Glossopteris: a fern found on the southern continents
Cynognathus: a land reptile found in South America and Africa
Lystrosaurus: a land reptile found in Africa, Antarctica, and India
Mesosaurus: a freshwater swimming reptile found in Africa and South America

6. Geologic Evidence From Rocks
Not only fossils provide evidence for theory support
Rocks in Africa and South America
When you examine the continents of Africa and South America,they look as if they could piece together like a puzzle
The layers of coal depth line up with each other
Rock deposits from glaciers also match

7. Naval oceanography made two significant contributions in the advancement of the theory of plate tectonics. .
1. The charting of the ocean floor using echo sounding refined the understanding of seafloor structure
2. Studies of the sea floor using instruments called magnetometers revealed strong evidence in support of seafloor spreading.
Just as maps of the oceans and coastlines initiated the idea of continental drift, maps of the ocean floor propelled science into the investigation of seafloor spreading. Charts and studies of the mid ocean ridge system, trenches, seamounts, and continental shelves—have been examined and catalogued.
Using these and other data, Harry Hess and Charles Dietz proposed the idea of seafloor spreading. They suggested that the worldwide system of undersea mountains called the mid-ocean ridges is where new ocean floor is created as plates move apart. As they diverge, they move large crustal plates along with the continents that sit atop of them.

8. Spreading Sea Floor Divergent Boundary Divergent Boundaries
Constructive-add new land
Mid-ocean Ridge
Ocean floor moves away on either side of the ridge
Called sea-floor spreading
Often offset by transform faults which causes a curve in the ridge
Sea-Floor Spreading/Mid-Ocean Ridge
Basic Plate Boundaries
Transform Faults

9. Magnetic Rock Strips
Some minerals (such as magnetite) have magnetic properties
These minerals line up with the Earth’s magnetic poles
When the molten rock hardens, a permanent record of the Earth’s magnetism remains
The Earth’s magnetic poles have reversed themselves from time to time
Animation
Sea Floor Spreading

10. Convergent Boundaries
Plates collide-destructive
Two continents colliding build mountains or plateaus
The Indian Plate and the Eurasian Plate collide to form the Himalayas which have Mt. Everest , the highest mountain on Earth.

11. Convergent Boundary
Destructive-crust is destroyed (melted by the mantle)
Called Subduction
When oceanic and continental crust collide
Oceanic crust is pushed down into the mantle and melted
Some of this melted material surges upward

12. Convergent Boundaries
The continental crust is also forced upward producing volcanoes
The Cascade Range in Washington and Oregon are an example of this
Convergent Boundaries

13. Convergent Boundaries
When two oceanic plates collide subduction occurs
The older denser plate is pushed into the mantle and melted
Some of the material rises upward and erupts on the ocean floor forming an island arc

14. Theory of Plate Tectonics
Tectonics: refers to the branch of geology that is concerned with plate movements
Theory of Plate Tectonics: Links together the ideas of continental drift and ocean floor spreading to explain how the Earth has evolved over time.
It explains the formation, movements, collisions, and destruction of the Earth’s crust
According to the theory the Earth’s uppermost layer, called the lithosphere, is made up of plates

15. Lithospheric Plates There are seven major plates
The Pacific Plate-
which covers 1/5 of the Earth
North American
South American
Eurasian
African
Indo-Australian
Antarctic Plates
There are also Many smaller plates
Caribbean
Arabian
Plate Tectonics Review

16. SUMMATION The theory of plate tectonics is relatively new
Early 1900s, Alfred Wegener first developed a theory of continental drift based on a collection of evidence from rocks and fossils found on continents separated by vast distances
1928, Arthur Holmes proposed a mechanism to explain how the continents could have moved across Earth's surface
Circular convection currents of molten material deep within Earth could provide ample force to divide and move continents
By the late 1960s, evidence of seafloor spreading helped to support the now well-accepted theory of plate tectonics.